The present invention is directed to a rolling protective shutter assembly which has a shutter curtain for covering a window or door opening that may be rolled up into a shutter housing when not in use, and in particular to a motor-driven shutter assembly configured to shut off the motor when the base slat is detected to be proximate the shutter housing, with the base slat being retained by the side tracks of the assembly to facilitate proper deployment of the shutter curtain when the motor operates to unroll the shutter curtain.
Rolling protective shutters are conventional and are used to provide protection against extreme weather conditions and to deter theft, for example. One such rolling protective shutter is disclosed in U.S. Pat. No. 4,345,635 to Solomon. As shown in FIGS. 1 and 2 of that patent, the Solomon shutter is composed of a plurality of elongate slats, each of which has a pair of circular ribs attached to its sides. The slats are interconnected by a plurality of elongate hinges, each of which has a pair of circular apertures in which the circular ribs of the slats are disposed. When the Solomon shutter is unrolled to its protective position, each of the slats in the shutter is disposed vertically with the ends of the slats disposed with guide channels or side tracks on either side of the opening. When not in use, the Solomon shutter may be rolled up into a housing disposed at the upper end of the protective shutter.
Another type of rolling protective shutter is disclosed in U.S. Pat. No. 5,365,990 to Ueda. As shown in FIGS. 2 and 3 of that patent, the Ueda shutter is composed of a plurality of slats, each of which has an upper rearward hook extending longitudinally along the upper edge of the slat and a lower U-shaped recess extending longitudinally along the lower edge of the slat. The recess has a forward horizontal projection on a rear edge and extending longitudinally so that when the lower slat moves down under gravity, the hook of the lower slat bears on the horizontal projection of the upper slat. The Ueda shutter may be rolled up and unrolled in a similar manner as the Solomon shutter.
In rolling shutter systems such as the Solomon and Ueda shutters, a portion of the shutter must remain within the side tracks to prevent the shutter from completely rolling up onto the take-up roll within the shutter housing. In some applications, the base slat has a handle extending outwardly from the shutter. One way to stop the bottom of the shutter from entering the housing is to size the opening in the housing through which the shutter passes narrow enough so that the handle hits the housing. The bottom of the shutter will stop short of entering the housing, but in many installations the housing is fabricated from sheet metal that is easily bent if the shutter is rolled up too rapidly.
In another alternative for stopping the bottom of the shutter, metal braces are attached to the side tracks and extend inwardly into the opening so that they engage the handle as the shutter is rolled up. Although the braces are stronger than the sheet metal housing, the handle and the braces can be damaged from repeated metal-on-metal impacts. Both the handle and the braces can be bent, gouged or broken, thereby increasing the possibility that the entire shutter will roll up into the housing and causing deterioration of the appearance of the shutter system. Additionally, the shutter may make a loud bang when the metal handle impacts the metal braces.
One solution for manually operated shutters is provided in U.S. Pat. No. 6,095,224 to Miller (hereinafter “the Miller '224 patent”). In the Miller '224 patent, portions of the side tracks of the assembly extend upwardly into the shutter housing and include spring biased stop members. Locking members extend outwardly from either end of the base slat and beyond the width of the shutter curtain such that the locking members are engaged by the stop members as they approach or enter the shutter housing. Configured in this way, the stopping mechanism is not visible and, consequently, does not diminish the aesthetic qualities of the shutter assembly, and reduces the noise created when the shutter curtain reaches its limiting position.
While effective with manual shutters, such mechanical mechanisms generally are not applicable in motor-driven shutter assemblies due to the risk of damaging the motor when a load is applied to the shutter curtain by the stop mechanism. In currently known motor-driven shutter assemblies, the base slat is required to stay in the side tracks and cannot fully retract into the housing. In many cases, the base slat remains in the side tracks below the bottom of the shutter housing by 3″ or more, thereby reducing the size of the opening. The side tracks do not extend upwardly into the shutter housing in a manner that would retain the base slat so that the remaining slats of the shutter curtain are free to roll up onto shutter support member. The base slat must remain in the side tracks in order to lead the slats back into the side tracks when the shutter curtain is unrolled, with gravity pulling the shutter into the tracks as the shutter curtain is dispensed from the shutter support member. Additional weights are sometimes required to guarantee that the shutter curtain will be dispensed correctly despite friction and other forces caused by the engagement of the shutter curtain by the components of the shutter assembly. If the base is retracted completely into the shutter housing, it may not find its way back into the side tracks.
In some implementations, the drive motors are provided with limit switches to attempt to cut off the motor when the shutter curtain is rolled up to a desired position. However, the limit switch typically operates based on the angular displacement of the shutter support member, and not the actual position of the shutter curtain. The position of the base slat can vary based on the tightness with which the shutter curtain is wrapped around the shutter support member. Additionally, an arrangement such as that shown in the Miller patent may be used with a motor driven shutter assembly to ensure that the base slat cannot be pushed up into the housing and out of the side tracks, and thereby causing a failure of the shutter assembly. If the shutter curtain equipped with the stopping mechanism rolls up slightly incorrectly, the limit switch on the motor may not be reached, thereby causing the shutter curtain and motor to be put under stress that can cause a failure of the curtain or the motor.
In other implementations, the drive motors are designed to sense when the shutter curtain is subjected to a load, and to shut off in response. The motors are specially made and adjusted to sense the correct torque at the stop position, and to not stop under the weight load of the shutter curtain when the curtain is drawing up. The motor also should not stop due to frictional forces that invariably will be present as the shutter curtain moves within the side tracks. These configurations still require the base slat to be at least partially disposed in the side tracks to function as a leader for the shutter curtain, and weight may need to be put in the base slat to ensure that the base slat moves downward in the side tracks to properly deploy the shutter curtain, and thereby affecting the adjustment of the drive motor. As can be seen, these solutions for motor driven shutter assemblies present performance risks relating to the proper deployment of the shutter curtain and potential damage to the shutter curtain and/or motor. Therefore, a need exists for an improved mechanism for stopping the motor when a particular part of the shutter curtain, such as the base slat, reaches the upper limit, and for allowing the base slat to be recessed within the shutter housing without compromising the ability of the shutter curtain to be unrolled back into the shutter tracks.